This invention relates to an improvement in the process for the manufacture of a morpholine compound from the reaction of a dialkylene glycol with ammonia in the presence of hydrogen and a hydrogenation catalyst whereby hydrogen and unreacted ammonia are recovered and reused in the process. The process for the manufacture of morpholines to which this invention is most particularly adaptable is described in U.S. Pat. No. 3,151,112 and is applicable to the broadest description thereof.
In such a process a dialkylene glycol described by the formula: ##STR1## wherein R, R' and R" are hydrogen, alkyl or aryl, is reacted with ammonia in the presence of hydrogen and a hydrogenation catalyst to produce a morpholine compound. Suitable dialkylene glycols include diethylene glycol, dipropylene glycol, di-1, 2-butylene glycol, di-2, 3-butylene glycol, and the like, and the term morpholine compound is used in the generic sense and is meant to include the compounds from which the name is derived and the carbon substituted alkyl and aryl derivatives thereof. For example, this term includes morpholine and its mono, di, tri, and tetra alkyl or aryl substituted derivatives.
The process for the manufacture of morpholine as described in the above-identified patent involves a reaction at elevated temperatures and pressures. The reaction broadly taught occurs at between about 150.degree. C to about 400.degree. C and in a pressure range from about 30 to about 400 atmospheres though this invention is just as applicable to similar processes operating at other conditions. The reaction of the dialkylene glycol with ammonia occurs in the presence of hydrogen which must be present at least in substantial amounts for the efficient conduct of the morpholine process. As stated in the patent, hydrogen should contribute from about 10 to about 200 atmospheres of the reaction pressure.
The practice of the process is carried out in the presence of a suitable catalyst, generally classified as hydrogenation catalysts, or in another sense hydrogenation-dehydrogenation catalysts, many of which are disclosed in said U.S. Pat. No. 3,151,112. However, it will be understood that the practice of the invention described and claimed herein is adaptable to any process for the manufacture of morpholine by reacting a dialkylene glycol with ammonia in the presence of a catalyst and a hydrogen since, under such conditions, it is necessary for the efficient and economic manufacture of the product to recover hydrogen and ammonia for recycle to the process. Ammonia is introduced into the reaction in a large excess and hydrogen is consumed only slightly if at all. Thus, recovery and recycle is necessary.
Previously this recovery has been accomplished by scrubbing the gas stream, comprised generally of hydrogen, methane and ammonia, with water to separate the ammonia from the hydrogen so that hydrogen could be returned to the reactor through a compressor which would restore the pressure of the hydrogen to the level at which the reaction is conducted. After scrubbing, the hydrogen, including the methane stream, is saturated with water. The presence of water in such a hydrogen stream complicates matters since water creates a corrosion problem and condenses when the hydrogen is compressed.
Further, when water scrubbing is used to remove the ammonia it is necessary to attempt to separate the ammonia from water scrubbing material prior to the recycling of the ammonia to the reactor. Thus, some ammonia is lost during the stripping of ammonia from water making it necessary to dispose of ammonia-contaminated water in a manner to protect the environment, often to the extent of incinerating the waste stream. This contributes to a loss in efficiency of the plant by requiring considerable additional energy and capital investment to accomplish an ecologically safe disposal of the waste material.
Accordingly, it is an object of this invention to provide a process whereby efficient use can be made of gases from the process of the manufacture of morpholine compounds from the catalytic reaction of a dialkylene glycol with ammonia in the presence of hydrogen. It is a further object of this invention to effect substantially quantitative recovery of ammonia from the process for recycling to the reactor.
It is still further objective of this invention to provide for the recovery of hydrogen in a substantially anhydrous condition for recycle to the reactor. It is yet another object of this invention to recover ammonia from the off gases of the morpholine process thereby avoiding the release of such material upon the environment.